On Thu, Sep 03, 2015 at 09:00:36AM +0200, Stéphane ANCELOT wrote:
> Hi,
>
> Do you think I can use the Intel integrated turbo boost mode, without
> problems.
>
> I have this nice processor :
> http://ark.intel.com/fr/products/76308/Intel-Core-i5-4300U-Processor-3M-Cache-up-to-2_90-GHz
Just experimented this, the turbo mode is a problem for applications
which rely on a precise relation between the actual count of cpu
cycles of a busy loop and the time. The sched_quota falls under that
category and simply does not work reliably when turbo mode is
enabled. Fortunately, it is possible to turn off turbo mode. For
that, in the kernel configuration
- enable CPU_FREQ
- choose performance mode by default
- enable intel pstate driver
- echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
Other than that, turbo mode does not seem to break the latency,
which would mean that the tsc frequency does not change with turbo
mode.
--
Gilles.
https://click-hack.org
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